The Messenger of Allah ﷺ forbade the earnings of the cupper.
نهي رسول الله ﷺ عن كسب الحجام.
No references are available.
Ibn Majah (2165) narrated it from Hisham bin Ammar, who said, Yahya bin Hamza narrated to us, who said, Uzai narrated to me, from Zuhri, from Abu Bakr bin Abdul-Rahman bin Harith bin Hisham, from Abu Masud Uqbah bin Amr, and he mentioned it. Its isnad is hasan because of Hisham bin Ammar, for his hadith is hasan, and Busiri declared it sahih in his Zawaid.